Synthesis of soluble functionalized lithium initiators

ABSTRACT

This invention discloses a process for making dilithium initiators in high purity. This process can be conducted in the absence of amines which is desirable since amines can act as modifiers for anionic polymerizations. The dilithium compounds made are highly desirable because they are soluble in aromatic solvents. The present invention also discloses a tire which is comprised of a generally toroidal-shaped carcass with an outer circumferential tread, two spaced beads, at least one ply extending from bead to bead and sidewalls extending radially from and connecting said tread to said beads, wherein said tread is adapted to be ground-contacting, and wherein said tread is a cured the rubber formulation which is comprised of (a) at least one rubbery polymer containing functional groups of the structural formula: 
                         
wherein R, R′ and R″ can be the same or different, wherein R is selected from the group consisting of hydrogen atoms, alkyl groups, aryl groups, alkaryl groups, and amino aryl groups, and wherein R′ and R″ represent alkyl groups alkyl groups that contain from 1 to 8 carbon atoms, and (b) at least one member selected from the group consisting of carbon black and silica.

This is a divisional and a continuation-in-part application of U.S.patent application Ser. No. 10/713,122, filed on Nov. 14, 2003 (nowissued as U.S. Pat. No. 7,166,747), which is a divisional of U.S. patentapplication Ser. No. 09/944,664, filed on Aug. 31, 2001 (now issued asU.S. Pat. No. 6,686,504), which claims the benefit of the priority ofU.S. Provisional Patent Application Ser. No. 60/229,494, filed on Aug.31, 2000.

BACKGROUND OF THE INVENTION

Lithium compounds are commonly used as initiators for anionicpolymerizations. Such organolithium initiators can be employed insynthesizing a wide variety of rubbery polymers. For instance,organolithium initiators can be used to initiate the anionicpolymerization of diolefin monomers, such as 1,3-butadiene and isoprene,into rubbery polymers. Vinyl aromatic monomers can, of course, also becopolymerized into such polymers. Some specific examples of rubberypolymers that can be synthesized using organolithium compounds asinitiators include polybutadiene, polyisoprene, styrene-butadiene rubber(SBR), styrene-isoprene rubber, and styrene-isoprene-butadiene rubber(SIBR).

The organolithium compounds that can be used to initiate such anionicpolymerizations can be either a specific organomonolithium compound orit can be a multifunctional type of initiator. In commercialapplications monolithium compounds are normally used because they areavailable as pure compounds that are soluble in organic solvents.Multifunctional organolithium compounds are not necessarily specificcompounds but rather represent reproducible compositions of regulablefunctionality. Many of such multifunctional organolithium compounds mustbe stored under refrigeration before being used.

U.S. Pat. No. 5,981,639 explains that multifunctional initiators used toinitiate anionic polymerizations include those prepared by reacting anorganomonolithium compounded with a multivinylphosphine or with amultivinylsilane, such a reaction preferably being conducted in an inertdiluent such as a hydrocarbon or a mixture of a hydrocarbon and a polarorganic compound. The reaction between the multivinylsilane ormultivinylphosphine and the organomonolithium compound can result in aprecipitate which can be solubilized if desired, by adding asolubilizing monomer such as a conjugated diene or monovinyl aromaticcompound, after reaction of the primary components. Alternatively, thereaction can be conducted in the presence of a minor amount of thesolubilizing monomer. The relative amounts of the organomonolithiumcompound and the multivinylsilane or the multivinylphosphine preferablyshould be in the range of about 0.33 to 4 moles of organomonolithiumcompound per mole of vinyl groups present in the multivinylsilane ormultivinylphosphine employed.

U.S. Pat. No. 5,981,639 further notes such multifunctional initiatorsare commonly used as mixtures of compounds rather than as specificindividual compounds. Other multifunctional polymerization initiatorscan be prepared by utilizing an organomonolithium compound, furthertogether with a multivinylaromatic compound and either a conjugateddiene or monovinylaromatic compound or both. These ingredients can becharged initially, usually in the presence of a hydrocarbon or a mixtureof a hydrocarbon and a polar organic compound as a diluent.Alternatively, a multifunctional polymerization initiator can beprepared in a two-step process by reacting the organomonolithiumcompound with a conjugated diene or monovinyl aromatic compound additiveand then adding the multivinyl aromatic compound. Any of the conjugateddienes or monovinyl aromatic compounds described can be employed. Theratio of conjugated diene or monovinyl aromatic compound additiveemployed preferably should be in the range of about 2 to 15 moles ofpolymerizable compound per mole of organolithium compound. The amount ofmultivinylaromatic compound employed preferably should be in the rangeof about 0.05 to 2 moles per mole of organomonolithium compound.Exemplary multivinyl aromatic compounds include 1,2-divinylbenzene,1,3-divinylbenzene, 1,4-divinylbenzene, 1,2,4-trivinylbenzene,1,3-divinylnaphthalene, 1,8-divinylnaphthalene,1,3,5-trivinylnaphthalene, 2,4-divinylbiphenyl, 3,5,4′-trivinylbiphenyl,m-diisopropenyl benzene, p-diisopropenyl benzene,1,3-divinyl-4,5,8-tributylnaphthalene and the like. Divinyl aromatichydrocarbons containing up to 18 carbon atoms per molecule arepreferred, particularly divinylbenzene as either the ortho, meta or paraisomer and commercial divinylbenzene, which is a mixture of the threeisomers, and other compounds, such as the ethylstyrenes, also is quitesatisfactory.

U.S. Pat. No. 4,196,154 discloses organic liquid soluble multifunctionallithium containing initiators are prepared by reacting an organo lithiumcompound with an organic compound containing at least one group of theconfiguration 1,3-bis(1-phenylethenyl)benzene. U.S. Pat. No. 4,196,154reports that such initiators can be prepared in the absence of polarsolvents and are very desirable for the polymerization of dienes such asbutadiene to a desirable 1,4 configuration.

SUMMARY OF THE INVENTION

This invention discloses a process for making dilithium initiators inhigh purity. This process can be conducted in the absence of amineswhich is desirable since amines can act as modifiers for anionicpolymerizations. The dilithium compounds made are highly desirablebecause they are soluble in aromatic solvents and do not need to bestored under refrigeration.

The present invention more specifically discloses a process forsynthesizing a dilithium initiator which comprises reactingdiisopropenylbenzene with a tertiary alkyl lithium compound in anaromatic solvent at a temperature which is within the range of about 0°C. to about 100° C.

The present invention further discloses a process for synthesizingm-di-(1-lithio-1-methyl-3,3-dimethylbutyl)benzene which comprisesreacting diisopropenylbenzene with tertiary-butyllithium in an aromaticsolvent at a temperature which is within the range of about 0° C. toabout 100° C.

The subject invention also discloses a process for synthesizing afunctionalized lithium initiator which comprises the steps of (1)reacting diisopropenylbenzene with a tertiary alkyl lithium compound inan aromatic solvent at a temperature which is within the range of about0° C. to about 100° C. to produce a dilithium initiator; and (2)reacting the dilithium initiator with a halide compound selected fromthe group consisting of (a) tin halides of the structural formula:

-   (b) silicon halides of the structural formula:

-   (c) amine halides of the structural formula:

-   and (d) phosphorus halides of the structural formula:

wherein X represents a halogen atom, and wherein R1, R2, and R3 can bethe same or different and represent alkyl groups, aryl groups, or alkoxygroups containing from 1 to about 10 carbon atoms.

The present invention also discloses a process for synthesizing afunctionalized lithium initiator which comprises the steps of (1)reacting diisopropenylbenzene with a tertiary alkyl lithium compound inan aromatic solvent at a temperature which is within the range of about0° C. to about 100° C. to produce a dilithium initiator; and (2)reacting the dilithium initiator with a compound having the structuralformula:

wherein X represents a neucleophile, and wherein R1, R2, and R3 can bethe same or different and represent alkyl groups, aryl groups, or alkoxygroups containing from 1 to about 10 carbon atoms. The neucleophile willtypically be selected from the group consisting of aldehydes, ketones,esters, halides, and acetals. Halides are typically preferred.

The present invention further discloses a process for synthesizing afunctionalized lithium initiator which comprises the steps of (1)reacting diisopropenylbenzene with a tertiary alkyl lithium compound inan aromatic solvent at a temperature which is within the range of about0° C. to about 100° C. to produce a dilithium initiator; and (2)reacting the dilithium initiator with a alkylaminoaryl compound of thestructural formula:

wherein R, R′, and R″ can be the same or different, wherein R isselected from the group consisting of hydrogen atoms, alkyl groups, arylgroups, alkaryl groups, and amino aryl groups, and wherein R′ and R″represent alkyl groups.

The present invention also reveals a process for synthesizing afunctionalized lithium initiator which comprises reacting a dilithiuminitiator with an alkylaminoaryl compound of the structural formula:

wherein R, R′, and R″ can be the same or different, wherein R isselected from the group consisting of hydrogen atoms, alkyl groups, arylgroups, alkaryl groups, and amino aryl groups, and wherein R′ and R″represent alkyl groups.

DETAILED DESCRIPTION OF THE INVENTION

Dilithium initiators can be synthesized using the process of thisinvention by reacting a tertiary-alkyl lithium compound withm-diisopropenylbenzene in an aromatic solvent. The aromatic solvent willtypically be an alkyl benzene. The alkyl group in the alkyl benzene willtypically contain from 1 to 8 carbon atoms. It is preferred for thealkyl group in the alkyl benzene solvent to contain from 1 to about 4carbon atoms. Some preferred aromatic solvents include toluene, ethylbenzene, and propyl benzene. Ethyl benzene is the most highly preferredaromatic solvent.

It is critical for a tertiary-alkyl lithium compound to be reacted withthe m-diisopropenylbenzene. The tertiary-alkyl lithium compound willtypically contain from 4 to about 8 carbon atoms. It is preferred forthe tertiary-alkyl lithium compound to be tertiary-butyl lithium.

The reaction will typically be conducted at a temperature that is withinthe range of about 0° C. to about 100° C. It is normally preferred forthe reaction between the tertiary-alkyl lithium and them-diisopropenylbenzene to be carried out at a temperature that is withinthe range of about 10° C. to about 70° C. It is typically more preferredfor the reaction temperature to be within the range of about 20° C. toabout 40° C.

A functionalized lithium initiator can be prepared by reacting adilithium initiator with a halide compound. Any dilithium initiator canbe employed. However, dilithium initiators that are synthesized byreacting a tertiary-alkyl lithium compound with m-diisopropenylbenzeneare highly preferred. The halide compound utilized will be selected fromthe group consisting of (a) tin halides of the structural formula:

-   (b) silicon halides of the structural formula:

-   (c) amine halides of the structural formula:

-   (d) phosphorus halides of the structural formula:

-   and (e) halides of the structural formula:

wherein X represents a halogen atom, and wherein R1, R2, and R3 can bethe same or different and represent alkyl groups, aryl groups, or alkoxygroups containing from 1 to about 10 carbon atoms. R1, R2, and R3 willtypically be alkyl groups containing from 1 to about 4 carbon atoms oralkoxy groups containing from 1 to 4 carbon atoms. It is preferred forR1, R2, and R3 to be methyl groups (CH3-), ethyl groups (CH3-CH2-),methoxy groups (CH3-O—), or ethoxy groups (CH3-CH2-O—).

A compound of the structural formula:

wherein X represents a neucleophile, and wherein R1, R2, and R3 can bethe same or different and represent alkyl groups, aryl groups, or alkoxygroups containing from 1 to about 10 carbon atoms, can be reacted withthe dilithium initiator in place of the halide compounds describedabove. In such compounds the neucleophile will typically be selectedfrom the group consisting of aldehydes, ketones, esters, halides, andacetals. Halides are typically preferred neucleophiles.

The alkylaminoaryl compounds that can be reacted with the dilithiumcompound are typically of the structural formula:

wherein R, R′, and R″ can be the same or different, wherein R isselected from the group consisting of hydrogen atoms, alkyl groups, arylgroups, alkaryl groups, and amino aryl groups, and wherein R′ and R″represent alkyl groups. It is typically preferred for R′ and R″ torepresent alkyl groups that contain from 1 to about 8 carbon atoms. Itis generally more preferred for R′ and R″ to represent alkyl groups thatcontain from 1 to about 4 carbon atoms, such as methyl groups, ethylgroups, propyl groups, and butyl groups. Highly preferred alkylaminoarylcompounds that can be utilized are of the structural formula:

wherein R′ and R″ can be the same or different and wherein R′ and R″represent alkyl groups. Some highly preferred alkylaminoaryl compoundsinclude N,N-dimethylaminobenzaldehyde and4,4′-bis(dimethylamino)benzophenone.

The functionalization reaction will typically be carried out at atemperature that is within the range of about −80° C. to about 150° C.However, to enhance the probability of mono-functionalization, whichreduces the probability of di-functionalization, the functionalizationreaction will preferably be carried out at a reduced temperature. It isaccordingly preferred for the functionalization reaction to be conductedat a temperature that is within the range of about −70° C. to about 20°C. It is normally more preferred for the functionalization reaction tobe conducted at a temperature that is within the range of about −60° C.to about 0° C. It is also preferred for the halide compound to be addedto a solution of the dilithium initiator (rather than adding thedilithium initiator to the halide compound).

The functionalized initiators made by utilizing the technique of thisinvention offer significant advantages when used to initiate the anionicpolymerization of diene monomers, such as 1,3-butadiene or isoprene,into rubbery polymers. For instance, such functionalized initiatorsoffer improved solubility in aliphatic solvents. More importantly, therubbery polymers made with such functionalized initiators offer improvedcompatibility in rubber formulations that contain silica and/or carbonblack. Such rubbery polymer can optionally be coupled with tin and/orsilicon compounds. For instance, such rubbery polymers can be coupledwith tin tetrachloride or silicon tetrachloride.

The synthesis of functionalized lithium initiators by the process ofthis invention by reacting a dilithium initiator with an alkylaminoarylcompound can be depicted as follows:

wherein A represents a hydrocarbon moiety, and wherein R, R′, and R″ canbe the same or different, wherein R is selected from the groupconsisting of hydrogen atoms, alkyl groups, aryl groups, alkaryl groups,and amino aryl groups, and wherein R′ and R″ represent alkyl groups.

The functionalized initiator made by this process can then be utilizedin the polymerization of conjugated diolefin monomers, such as1,3-butadiene or isoprene, or optionally the copolymerization ofconjugated diolefin monomers with vinyl aromatic monomers, such asstyrene or α-methyl styrene. Anionic polymerizations that are conductedutilizing such monomers can be depicted as follows:

wherein P represents the polymer chain made by the polymerization,wherein A represents a hydrocarbon moiety, wherein R, R′, and R″ can bethe same or different, wherein R is selected from the group consistingof hydrogen atoms, alkyl groups, aryl groups, alkaryl groups, and aminoaryl groups, and wherein R′ and R″ represent alkyl groups.

The living polymer made by this process can be killed by exposure towater or an alcohol. The reaction of such polymers with water can bedepicted as follows:

Accordingly, the functionalized rubbery polymers made by the process ofthis invention contain functional groups of the structural formula:

This invention is illustrated by the following examples that are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

EXAMPLE 1

In this example, a stable and hydrocarbon soluble dilithio initiator wasprepared. Neat m-diisoproprenylbenzene (100 mmoles) was added, undernitrogen, to a dried quart (0.95 liter) bottle containing 400 ml ofreagent grade ethylbenzene at room temperature. Then tert-butyllithium(in hexanes) was added in four portions of 50 mmoles with constantshaking. It was left at room temperature for two hours after theaddition of the tert-butyllithium was completed. The bottle containingthe reaction mixture was then rotated in a polymerization bath at 65° C.bath for two hours. After removing it from the bath, it was left to coolat room temperature. The resulting reddish brown solution containingdilithio initiator was titrated using the Gilman double titration methodfor active lithium. The GC-MS analysis of the hydrolyzed (with D20)product indicated that more than 95% dilithio species was formed.

EXAMPLE 2

In this experiment, the dilithium compound synthesized by the proceduredescribed in Example 1 was used to initiate the polymerization of1,3-butadiene monomer into polybutadiene rubber. In the procedure used,2300 g of a silica/amumina/molecular sieve dried premix containing 20weight percent of 1,3-butadiene in hexanes was charged into a one-gallon(3.8 liters) reactor. Then, 19.6 ml of 0.234 M dilithio initiator(Di-Li) was added to the reactor. The target number averaged molecularweight (Mn) was 100,000.

The polymerization was carried out at 75° C. for two hours. The GCanalysis of the residual monomers contained in the polymerizationmixture indicated that the 100% of monomer was converted to polymer. Thepolymerization was then shortstopped with ethanol and the polymer cementwas then removed from the reactor and stabilized with 1 phm ofantioxidant. After evaporating hexanes, the resulting polymer was driedin a vacuum oven at 50° C.

The polybutadiene produced was determined to have a glass transitiontemperature (Tg) at −99° C. It was also determined to have amicrostructure, which contained 8 percent 1,2-polybutadiene units, 92percent 1,4-polybutadiene units. The Mooney viscosity (ML-4) at 100° C.for this polymer was also determined to be 44. It was determined by GPCto have a number average molecular weight (Mn) of 193,000 and a weightaverage molecular weight (Mw) of 198,000. The MWD (Mw/Mn) of thispolymer was 1.03. This example clearly validated the formation ofdilithio species in the Example I since the molecular weight of thepolymer was double of the target value.

EXAMPLE 3

In this example, a telechlic functionalized polybutadiene containing4,4′-bis(diethylamino) benzophenol functional groups on both polymerchain ends was prepared. The procedure described in Example 2 wasutilized in these examples except that two molar quantity (to Di-Li) of4,4′-bis(diethylamino) benzophenone was added to the live cement afterthe polymerization of 1,3-butadiene was completed. The Tg andmicrostructures of this functionalized PBd were identical to polymermade in Example 2. The Mooney viscosity (ML-4) at 100° C. for thispolymer was 48.

EXAMPLE 4

In this example, a telechlic functionalized styrene-butadiene rubber(SBR) containing tributyl tin groups on both polymer chain ends wasprepared. The procedure described in Example 2 was utilized in theseexamples except that a premix containing styrene/1,3-butadiene inhexanes was used as the monomers and the styrene to 1,3-butadiene ratiowas 15:85. In addition, 0.75 molar ratio of TMEDA(N,N,N′,N′-tetramethylethylenediamine) to di-lithium was used as themodifier. Two molar quantities (to di-lithium) of t-butyltin chloridewas added to the live cement after the polymerization ofstyrene/1,3-butadiene was completed. The glass transition temperature(Tg) of this functionalized SBR was determined to be −45° C. The Mooneyviscosity (ML-4) at 100° C. for this polymer was determined to be 45.

EXAMPLE 5

In this example, a telechlic tin-coupled styrene-butadiene rubber (SBR)at both polymer chain ends was prepared. The procedure described inExample 4 was utilized in this example except that the target numberaverage molecular weight (Mn) was 75,000 instead of 100,000. Tintetrachloride was added the live cement after the polymerization ofstyrene/1,3-butadiene was completed. The Tg of this functionalized SBRwas determined to be −45° C. The Mooney viscosity (ML-4) at 100° C. forthe coupled SBR was 88 while the uncoupled base polymer (precursor priorto coupling) was 30.

EXAMPLE 6

In this experiment, 1000 grams of a silica/amumina/molecular sieve driedpremix of styrene and 1,3-butadiene in hexanes containing 20 weightpercent monomer was charged into a one-gallon (3.8 liter) reactor. Theratio of styrene to 1,3-butadiene was 20:80. Copolymerization wasinitiated by charging sodium dedecylbenzene sulfonate and the dilithiuminitiator made in Example 1 to the reactor at a molar ratio of 0.25:1.The copolymerization was allowed to continue at 70° C. until all ofthe-monomer was consumed (for about one hour). Then an additional 1000grams of monomer premix and N,N,N′,N′-tetramethylethylene-diamine(TMEDA) was charged into the reactor containing the living polymercement. The monomer premix added contained 40% styrene and 60%1,3-butadiene. The molar ratio of TMEDA to dilithium initiator was 5:1.The copolymerization was allowed to continue at 70° C. for an additionalhour until the monomers were essentially exhausted. Then thecopolymerization was shortstopped and the polymer was stabilized by theaddition of an antioxidant. The SBR made was then recovered and dried ina vacuum oven. The SBR had two glass transition temperatures at −75° C.(center block) and −20° C. (outer blocks).

EXAMPLE 7

In this example, a soluble functionalized lithium initiator containingtrimethyltin groups was prepared. In the procedure used, 34 ml of 1 M oftrimethyltin chloride (in hexane) was added with a syringe to a quart(0.95 liter) bottle containing 200 ml of 0.34 M1,3-bis(1-lithio-1,3,3′-trimethylbutyl) benzene (in ethyl benzene). Themixture was shaken at room temperature for about two hours. Theresulting mono-lithio initiator,1-(1-lithio-1,3,3′-trimethylbutyl)-3-(1-trimethyltin-1,3,3′-trimethylbutyl)benzenewas determined by Gilman titration to be 0.13 M.

EXAMPLES 8-10

In these examples, soluble mono-lithio initiators containingtributyltin, tributylsilyl, 2-(N,N-dimethylamino)ethyl functional groupswere prepared using the same procedures as described in Example 7 exceptthat that tributyltin chloride, tributylsilicon chloride and2-(N,N-dimethylamino) ethyl chloride were use in place of trimethyltinchloride.

EXAMPLE 11

In this experiment, a polybutadiene containing a trimethyltin functionalgroup was prepared. In the procedure used, 2300 g of asilica/amumina/molecular sieve dried premix containing 20 weight percentof 1,3-butadiene in hexanes was charged into a one-gallon (3.8 liters)reactor. 35.3 ml of 0.13 M a mono functionalized initiator,1-(1-lithio-1,3,3′-trimethylbutyl)-3-(1-trimethyltin-1,3,3′-trimethylbutyl)benzene was added to the reactor. The targetnumber averaged molecular weight (Mn) was 100,000.

The polymerization was carried out at 75° C. for 2.5 hours. The GCanalysis of the residual monomers contained in the polymerizationmixture indicated that the 100% of monomer was converted to polymer. Thepolymerization was then shortstopped with ethanol and the polymer cementwas then removed from the reactor and stabilized with 1 phm ofantioxidant. The polymer was then recovered by evaporation of thehexanes solvent. The resulting polymer was dried in a vacuum oven at 50°C.

The polybutadiene produced was determined to have a glass transitiontemperature (Tg) at −99° C. It was also determined to have amicrostructure that contained 9 percent 1,2-polybutadiene units and 91percent 1,4-polybutadiene units. The Mooney viscosity (ML-4) at 100° C.for this polymer was also determined to be 55.

EXAMPLE 12

In this example, a soluble functionalized lithium initiator containingdimethylaminophenyl was prepared. 34 ml. of 1 Mp-dimethylaminobenzaldehyde (in toluene) was added, via a syringe, to aquart bottle containing 200 ml. of 0.34 M1,3-bis(1-lithio-1,3,3-trimethylbutyl) benzene (in cyclohexane) at roomtemperature. The mixture was shaken at room temperature for an hour. Theresulting mono-lithio initiator,1-(1-lithio-1,3,3-trimethylbutyl)-3-(1-(p-dimethylaminophenyl,lithioxy)methyl)-1,3,3-trimethylbutyl)benzene was determined by Gilmantitration to be 0.15 M.

EXAMPLE 13

In this example, a soluble mono-lithio initiators containingbis-(dimethylaminophenyl) functional groups was prepared using the sameprocedure as described in Example 12 except that4,4′-bis-(dimethylamino)benzophenone (Michler's ketone) was used inplace of p-dimethylamino benzaldehyde.

EXAMPLE 14

In this experiment, a 15/85 styrene-butadiene rubber (SBR) containing a1-(4-dimthylaminophenyl)-1-hydroxymethyl functional group was prepared.2300 g of a silica/amumina/molecular sieve dried premix containing 20weight percent of 1,3-butadiene and styrene in hexanes was charged intoa one-gallon (3.8 liters) reactor. The ratio of styrene to 1,3-butadienewas 15:85. 16.1 ml. of 0.15 M a mono functionalized initiator,1-(1-lithio-1,3,3-trimethylbutyl)-3-(1-(p-dimethylaminophenyl,lithioxy)methyl)-1,3,3-trimethylbutyl)benzene was added to the reactor.The target number averaged molecular weight (Mn) was 200,000.

The polymerization was carried out at 70° C. for 1.5 hours. The GCanalysis of the residual monomers contained in the polymerizationmixture indicated that the 100% of monomer was converted to polymer. Thepolymerization was then shortstopped with ethanol and the polymer cementwas then removed from the reactor and stabilized with 1 phm ofantioxidant. After the hexanes solvent, the resulting polymer was driedin a vacuum oven at 50° C.

The SBR produced was determined to have a glass transition temperature(Tg) at −38° C. It was also determined to have a microstructure, whichcontained 52 percent 1,2-polybutadiene units, 33 percent1,4-polybutadiene units and 15% random polystyrene units. The Mooneyviscosity (ML-4) at 100° C. for this polymer was also determined to be73.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention.

1. A tire tread rubber composition which is comprised of (a) at leastone rubbery polymer which is synthesized using a functionalized lithiuminitiator, wherein the functionalized initiator is made by a processwhich comprises (i) reacting m-diisopropenylbenzene with a tertiaryalkyl lithium compound in an aromatic solvent at a temperature which iswithin the range of about 0° C. to about 100° C. to produce a dilithiuminitiator and (ii) reacting the dilithium initiator with analkylaminoaryl compound of the structural formula:

wherein R, R′, and R″ can be the same or different, wherein R isselected from the group consisting of hydrogen atoms and alkyl groups,and wherein R′ and R″ represent alkyl groups, and (b) at least onemember selected from the group consisting of carbon black and silica. 2.A tire tread rubber composition as specified in claim 1 wherein saidrubbery polymer is coupled with at least one member selected from thegroup consisting of silicon halides and tin halides.
 3. A tread rubbercomposition as specified in claim 1 wherein R represents a hydrogen atomand wherein R′ and R″ represent methyl groups.
 4. A tread rubbercomposition as specified in claim 1 wherein the alkyl groups containfrom 1 to about 8 carbon atoms.
 5. A tread rubber composition asspecified in claim 1 wherein the alkyl groups contain from 1 to about 4carbon atoms.
 6. A tire tread rubber composition which is comprised of(a) at least one rubbery polymer which is synthesized using afunctionalized lithium initiator, wherein the functionalized initiatoris made by a process which consists of reacting a dilithium initiatorwith an alkylaminoaryl compound of the structural formula:

wherein R, R′, and R″ can be the same or different, wherein R isselected from the group consisting of hydrogen atoms and alkyl groups,and wherein R′ and R″ represent alkyl groups, and (b) at least onemember selected from the group consisting of carbon black and silica. 7.A tire tread rubber composition as specified in claim 6 wherein thedilithium initiator is made by (i) reacting m-diisopropenylbenzene witha tertiary alkyl lithium compound in an aromatic solvent at atemperature which is within the range of about 0° C. to about 100° C. 8.A tire tread rubber composition as specified in claim 7 wherein Rrepresents a hydrogen atom.
 9. A tire tread rubber composition asspecified in claim 7 wherein R represents an alkyl group.
 10. A tiretread rubber composition as specified in claim 8 wherein R′ and R″represent methyl groups.
 11. A tire tread rubber composition asspecified in claim 1 wherein the member selected from the groupconsisting of carbon black and silica is silica.
 12. A tire tread rubbercomposition as specified in claim 6 wherein the member selected from thegroup consisting of carbon black and silica is silica.
 13. A tire treadrubber composition as specified in claim 1 wherein them-diisopropenylbenzene is reacted with the tertiary alkyl lithiumcompound at a temperature which is within the range of about 10° C. toabout 70° C.
 14. A tire tread rubber composition as specified in claim 1wherein the m-diisopropenylbenzene is reacted with the tertiary alkyllithium compound at a temperature which is within the range of about 20°C. to about 40° C.
 15. A tire tread rubber composition as specified inclaim 1 wherein said rubbery polymer is coupled a silicon halide.
 16. Atire tread rubber composition as specified in claim 1 wherein saidrubbery polymer is coupled a tin halide.
 17. A tire tread rubbercomposition as specified in claim 16 wherein the tin halide is of thestructural formula:

wherein X represents a halogen atom, and wherein R₁, R₂, and R₃ can bethe same or different and represent alkyl groups, aryl groups, or alkoxygroups containing from 1 to about 10 carbon atoms.
 18. A tire treadrubber composition as specified in claim 15 wherein the silicon halideis of the structural formula:

wherein X represents a halogen atom, and wherein R₁, R₂, and R₃ can bethe same or different and represent alkyl groups, aryl groups, or alkoxygroups containing from 1 to about 10 carbon atoms.
 19. A tire treadrubber composition as specified in claim 17 wherein R₁, R₂, and R₃represent alkyl groups containing from 1 to about 4 carbon atoms oralkoxy groups containing from 1 to 4 carbon atoms.
 20. A tire treadrubber composition as specified in claim 17 wherein R₁, R₂, and R₃ areselected from the group consisting of methyl groups, ethyl groups,methoxy groups, and ethoxy groups.